The present invention relates to a multiple-needle pattern-stitching sewing machine which is capable of forming patterns in zigzag, etc. as a plurality of the same stitch traces.
Conventionally, as a zigzag sewing machine, a single-needle sewing machine has been known which comprises a sewing needle capable of vertical reciprocating movement and laterally-swinging movement and other means moving in coupling with this sewing needle.
In a multiple-needle sewing machine, the mechanism will be complicated if we make multiple-needles simultaneously laterally movable as the single needle. For this reason, one type of multiple-needle sewing machine forms stitch traces on a cloth by swinging laterally a cloth held between a needle plate and a cloth holder. In such a multiple-needle sewing machine, the needle-passing hole is made long enough for the needle plate moving right and left without hitting the needle.
The above-mentioned conventional multiple-needle sewing machine has the following disadvantages.
In the multiple-needle sewing machine which has the needle-passing hole formed as a long hole, when many needles simultaneously pierce into a cloth, this piercing force will push the cloth into the long hole, making stitching impossible or, even if possible, stitch lines so distorted that no neat stitch traces are formed.
As a countermeasure, the cloth is stretched on a frame to be sewn without being loosened, or is backed up with a thick paper before being sewn.
However, in these methods, as pretreatments before sewing, work is required to stretch the cloth on a frame or back up the cloth with a thick paper, etc. In addition, after sewing, it is necessary to detach the cloth from the frame or remove the back-up thick paper. These jobs are troublesome and tedious. No neat stitch traces may be obtained. Further, no mass production system is applicable.
Under such a situation, actually, multiple-needle sewing machines have hardly been applied to formation of patterns in zigzag, etc.